A wireless network is configured of an access point (AP) and a plurality of stations (STAs), wherein the AP transmits and receives data to and from the STAs through a wireless channel. After each data transmission from STAs, an acknowledge receipt (ACK) should be send back after a time interval of a short interframe space (SIFS). There is no problem when the AP only has an ACK packet to transmit. However, if the AP has both ACK and data to transmit, the transmission performance of the wireless network may be degraded.
That is, since the ACK has higher priority than data, the AP first transmits the ACK and then, transmits data. In this case, the AP transmits data to the STAs after wireless channel contention and DCF interframe space (DIFS) time elapse. The data transmission is delayed due to the interval of the channel contention and the DIFS time, such that data amount that can be processed in the wireless network is remarkably reduced, thereby degrading the transmission performance.
To solve this problem, a piggybacking scheme, which piggybacks the ACK on a MAC protocol data unit (MPDU) and the MPDU on which the ACK is piggybacked is transmitted at a low data bit rate so as to secure stability and reliability of the ACK transmission, is proposed. However, the MPDU needs to be transmitted at a low data bit rate so as to secure the stability and reliability of the ACK transmission even if the data may be transmitted at a high-speed bit rate, such that the transmission performance of the wireless network may be remarkably degraded.